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Comment by elnate | Hacker News Reader

Are there cameras capable of taking pictures in a broader spectrum of colours available for less than a small fortune? I'd like to see photos taken infrared - ultraviolet 'compressed' into our red-blue range.

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Although cameras have built-in filters that block UV and IR light, the IR portion is often weak and allows some light through. By adding a filter[1] that blocks visible light, there is often enough IR left to expose a photo[2]. With some caveats[3], it can be a cheap way to see the world in a different part of the spectrum.

[1] Hoya R72 for example

[2] A tripod is usually necessary since only a fraction of the light makes it through the filters. Even in bright sunlight a long exposure time may be required.

[3] Not all lenses work well in IR. Some have internal reflections that lead to "hot spots" or white patches, and some have bad optics for IR that causes blur. Similarly, some cameras' IR cut filters are too strong to be useable.

The CMOS and CCD sensors in digital cameras are sensitive to infrared and (near) UV. These sensors nearly always come with infrared and UV filters to keep them from recording things you don't see. If you are willing and able to hack your camera you can remove this filter to create a camera sensitive from near UV to true IR, ca. 200nm to 900 nm. You'll have to change the lens to make use of the UV part of the spectrum as optical glass blocks most of it.

This answer on PSE gives a nice overview: http://photo.stackexchange.com/questions/2262/are-digital-se...

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